The present invention relates to implantable heart stimulators generally, and more particularly to implantable anti-tachycardia pacemakers.
Typically, implantable anti-tachycardia pacemakers have the capability of providing a variety of anti-tachycardia pacing regimens. Normally, these regimens are applied according to a pre-programmed sequence, and each extends over a series of predetermined number of pacing pulses. After the series of pacing pulses is delivered, the devices check to determine whether the series of pulses was effective in terminating the detected tachyarrhythmia. Typically, termination is confirmed by a return to sinus rhythm, for example in response to a sequence of a predetermined number of spontaneous depolarizations separated by greater than a defined interval. In the absence of detected termination, delivery of a subsequent series of pacing pulses having modified pulse parameters, e.g. reduced inter-pulse interval, occurs in response to a redirection of tachycardia, using criteria similar to that employed to originally detect tachycardia, but in most cases based on less stringent criteria. Devices which function according to the basic methodology described above are disclosed in U.S. Pat. No. 4,830,006 issued to Haluska et al., U.S. Pat. No. 5,836,971 issued to Starkweather and U.S. Pat. No. 5,846,263 issued to Peterson et al.